using javascript to add form fields

Ok, so here is what I'm trying to do. The user will have a row of input fields and I want to have an add more button to add another row of fields. I have no idea how to do this. Here is an example of what I'm trying to accomplish.[img src=\"http://www.absolute-design.net/websites/calcoaero/images/example.jpg\" border=\"0\" alt=\"IPB Image\" /]